The present invention relates generally to elongated working platforms and in particular to an elevating platform assembly of the type having a rack and pinion drive mechanism.
Elongated working platforms are well known in the art and are commonly used during construction to support workers and equipment at desired elevations. Platforms of this nature include stationary scaffolding as well as moveable elevating platform assemblies. Although stationary scaffolding is useful, in many instances it is desired to change quickly the elevation of workers and equipment and thus, elevating platform assemblies are advantageous.
One known type of elevating platform assembly is manufactured by Hydro Mobile of L""Assomption, Quebec. This elevating platform assembly includes an elevating platform that is supported at one end by a mast. A drive mechanism acts between the elevating platform and the mast. The drive mechanism includes a trolley moveable along the mast to which the platform is secured. A motor is mounted on the trolley and drives pinions that cooperate with a rack secured to the mast. In this manner, the elevating platform can be moved upwardly and downwardly along the mast.
Although this elevating platform assembly works satisfactorily, when heavy loads are placed on the elevating platform near its end furthest from the mast, significant torque can be applied to the trolley by the elevating platform. The torque applied to the trolley acts to pull the trolley away from the mast. If the trolley moves relative to the mast under the influence of the torque, misalignment between the teeth of the pinions and the teeth of the rack results. This of course can result in stripping of the pinions as the trolley is advanced along the mast. As will be appreciated improvements to elevating platform assemblies of this nature are desired.
It is therefore an object of the present invention to provide a novel elevating platform assembly of the type having a rack and pinion drive mechanism.
According to one aspect of the present invention there is provided an elevating platform assembly comprising:
a generally vertical mast having a generally vertical rack mounted thereon;
a first trolley coupled to said mast and being moveable therealong;
a drive mechanism carried by said first trolley, said drive mechanism including at least one pinion in mating engagement with said rack; and
an elongated elevating platform extending from said mast and having a second trolley mounted adjacent one end thereof, said second trolley coupling said elevating platform to said mast and being moveable along said mast, wherein said first trolley is coupled to at least one of said second trolley and said elevating platform in a manner to maintain alignment of said at least one pinion and rack when loads are placed on said elevating platform that create moments at said mast.
In one embodiment, the first trolley is coupled to the elevating platform via a shock absorbing arrangement that includes an elastomeric element. The shock absorbing arrangement permits the elevating platform to pivot relative to the first trolley without significant forces being applied to the first trolley that act to pull the first trolley away from the mast.
In another embodiment, the first trolley is positioned on the mast below the second trolley and is coupled to the second trolley through shock absorbing elements carried by at least one of the first and second trolleys.
According to another aspect of the present invention there is provided an elevating platform assembly comprising:
an upright mast having a vertical rack extending along at least one side thereof;
a motor trolley coupled to said mast, said motor trolley carrying a drive mechanism including at least one rotatable pinion in mating engagement with said rack, rotation of said at least one pinion advancing said motor trolley vertically along said mast;
an elongated elevating platform extending from said at least one side of said mast, said elevating platform including a generally horizontal work surface; and
a main trolley acting between said elevating platform and said mast and being moveable vertically along said mast, wherein said motor trolley is coupled to one of said main trolley and said elevating platform in a manner so as to maintain alignment of said at least one pinion and said rack when loads are placed on said elevating platform.
The present invention provides advantages in that the coupling between the first trolley and either the second trolley or the elevating platform inhibits the at least one pinion from becoming misaligned with the rack when loads are placed on the elevating platform that create moments at the mast. By maintaining the at least one pinion and rack in alignment regardless of loads placed on the elevating platform, the likelihood of stripping of the teeth on the at least one pinion is reduced.